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Structure of the nociceptin/orphanin FQ receptor in complex with a peptide mimetic


Members of the opioid receptor family of G-protein-coupled receptors (GPCRs) are found throughout the peripheral and central nervous system, where they have key roles in nociception and analgesia. Unlike the ‘classical’ opioid receptors, δ, κ and μ (δ-OR, κ-OR and μ-OR), which were delineated by pharmacological criteria in the 1970s and 1980s, the nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP, also known as ORL-1) was discovered relatively recently by molecular cloning and characterization of an orphan GPCR1. Although it shares high sequence similarity with classical opioid GPCR subtypes (60%), NOP has a markedly distinct pharmacology, featuring activation by the endogenous peptide N/OFQ, and unique selectivity for exogenous ligands2,3. Here we report the crystal structure of human NOP, solved in complex with the peptide mimetic antagonist compound-24 (C-24) (ref. 4), revealing atomic details of ligand–receptor recognition and selectivity. Compound-24 mimics the first four amino-terminal residues of the NOP-selective peptide antagonist UFP-101, a close derivative of N/OFQ, and provides important clues to the binding of these peptides. The X-ray structure also shows substantial conformational differences in the pocket regions between NOP and the classical opioid receptors κ (ref. 5) and μ (ref. 6), and these are probably due to a small number of residues that vary between these receptors. The NOP–compound-24 structure explains the divergent selectivity profile of NOP and provides a new structural template for the design of NOP ligands.

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Figure 1: Structural overview of the NOP receptor.
Figure 2: The orthosteric ligand-binding pocket.
Figure 3: Molecular docking in the orthosteric-binding pocket.
Figure 4: Conformational differences in the ligand-binding pocket between NOP–C-24 and κ-OR–JDTic.

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Accession codes

Primary accessions

Protein Data Bank

Data deposits

The coordinates and the structure factors have been deposited in the Protein Data Bank under accession code 4EA3.


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This work was supported by PSI:Biology grant U54 GM094618 for biological studies and structure production, NIH Roadmap grant P50 GM073197 for technology development and R01 DA017204, R01 DA27170, and the NIMH Psychoactive Drug Screening Program (X.-P.H., E.V. and B.L.R.) and the Michael Hooker Chair of Pharmacology (B.L.R.), University of Ferrara (FAR grant to G.C.), Italian Ministry of University (FIRB Futuro in Ricerca 2010 grant to C.T.). We thank J. Francis for suggesting the idea to pursue the NOP receptor; J. Velasquez for help on molecular biology; T. Trinh, K. Allin and M. Chu for help on baculovirus expression; A. Walker and E. Abola for assistance with manuscript preparation; J. Smith, R. Fischetti and N. Sanishvili for assistance in development and use of the minibeam and beamtime at GM/CA-CAT beamline 23-ID at the Advanced Photon Source, which is supported by National Cancer Institute grant Y1-CO-1020 and National Institute of General Medical Sciences grant Y1-GM-1104.

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Authors and Affiliations



A.A.T. optimized the constructs, purified and crystallized the receptor in LCP, optimized crystallization conditions, grew crystals for data collection, collected the data and refined the structure, and prepared the manuscript. W.L. assisted with LCP experiments, performed fluorescence recovery after photobleaching assays, collected diffraction data, and assisted with preparing the manuscript. E.C. assisted in construct optimization, assisted with LCP experiments, collected diffraction data, and assisted with preparing the manuscript. V.K. performed the receptor docking and prepared the manuscript. H.W. assisted with membrane preparations, provided advice on crystallization strategies, and assisted with preparing the manuscript. E.V. and X.-P.H. performed ligand-binding and site-directed mutagenesis studies. C.T., R.G. and G.C. suggested the use of and synthesized numerous ligands for crystallization and pharmacological studies, and assisted with preparing the manuscript. B.L.R. supervised the pharmacology and mutagenesis studies and prepared the manuscript. V.C. assisted with the crystallization in LCP, collected diffraction data, processed diffraction data, and prepared the manuscript. R.C.S. was responsible for the overall project strategy and management and wrote the manuscript.

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Correspondence to Raymond C. Stevens.

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Competing interests

R.C.S. is a founder and Board of Directors member of Receptos, a GPCR drug discovery company.

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This file contains Supplementary Tables 1-5, Supplementary Figures 1-8 and additional references.The correct Supplementary Information was added on 29th May 2012. (PDF 1713 kb)

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Thompson, A., Liu, W., Chun, E. et al. Structure of the nociceptin/orphanin FQ receptor in complex with a peptide mimetic. Nature 485, 395–399 (2012).

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